Current inhalation therapy requirements vary over a wide range. For example, high-oxygen concentration streams are occasionally required for short durations, but the longer term care generally demands low oxygen gas. But the total gas volume needs of the patient (air plus oxygen) remains nearly constant. These broad requirements necessitate an aspirator device with a high degree of flexibility in effecting the desired composition and flow rate.
Moreover, moderate back pressures caused by patient exhalation together with the use of long, small-diameter delivery tubes could beneficially be overcome by a device capable of providing necessary gas volumes.